1. Field of the Invention
The present invention relates to a fixing device for a wet type master sheet making apparatus for making a master sheet, and particularly relates to an improvement to a device described in Japanese patent application Nos. 9-82074 and 9-289046.
2. Description of the Related Art
As is known in the prior art, in a wet type master sheet making apparatus for making a master sheet, an electrostatic latent image on the surface of the master sheet is developed by a developing liquid. After being developed, extra developing liquid is removed by a rinse squeezing device, and then a toner image is fixed and dried by a fixing device.
FIG. 7 shows the fixing device for the wet type master sheet making apparatus. The fixing device has a pre-heating panel heater B and a drying panel heater C on a fixing device frame, the pre-heating panel heater B and the drying panel heater C being aligned in the transporting direction of the master sheet X. The master sheet X is transported from the rinse squeezing device (not shown), and then transported by intermediate transporting rollers D and exit transporting rollers E. While the master sheet X is transported by the rollers D and E, the toner image on the surface of the master sheet X is fixed and dried. In FIG. 7, "F" shows pressure rollers for pressing the master sheet X toward the drying panel heater C.
In the fixing device shown in FIG. 7, the master sheet X which is transported from the rinse squeezing device includes moisture. Particularly, the back surface includes liquid including extra toner.
Therefore, when the master sheet X is pre-heated and dried by the pre-heating panel heater B and the drying panel heater C, the extra toner is transferred from the back surface of the master sheet X to the surface b of the heater B and the surface c of the heater C, and then a mass of the extra toner may deposit on the surfaces b and c.
If a mass of the extra toner is deposited on the surfaces b and c, the leading edge of the master sheet X may impact against the mass of the extra toner on the surfaces b and c. If the leading edge of the master sheet X impacts against the mass of the extra toner on the surfaces b and c, the maester sheet X may be jammed, or the mass of the extra toner may peel off from the surfaces b and c, and may be deposited on the surface or the back surface of the master sheet X. If the mass of the extra toner is deposited on the surface or the back surface of the master sheet X, the master sheet X is contaminated, or another master sheet adjoining the master sheet X on the stacker may be contaminated.
If the master sheet X is contaminated, a sheet to be printed is contaminated by the contaminated master sheet x when the sheet to be printed is offset printed.
In order to solve the above problem, a fixing device described in Japanese patent application No. 9-82074 has a cleaning web placed on the surface of the panel heater. The cleaning web is gradually fed in a direction opposite to the master sheet transporting direction, and absorbs the extra toner on the back surface of the master sheet. The cleaning web can prevent the back surface of the master sheet and the surface of the panel heater being contaminated. However, it is difficult to attach the cleaning web to the fixing device.
The cleaning web must be tensioned on the surface of the panel heater. When a new cleaning web replaces an old cleaning web, an electromagnetic solenoid is remote controlled to tension the cleaning web in an inching device described in Japanese patent application No. 9-82074.
However, it is troublesome to remote control the solenoid to tension the cleaning web. Further, it is difficult for a beginner to replace a cleaning web and to tense the cleaning web. In order to solve the above problem, a fixing device described in Japanese patent application No. 9-289046 is provided.
However, because the fixing device described in Japanese patent application No. 9-289046 has a pre-heating panel heater and a drying panel heater, the fixing device described in Japanese patent application No. 9-289046 cannot be applied to the small fixing device which has a cleaning web.